Haruo Isono

Flicker-Free Field-Sequential Stereoscopic TV System and Measurement of Human Depth Perception

This article describes a new system of presenting television programs in 3-D using ferroelectric liquid crystal shutter (LCS) glasses, and some findings of psychovisual experiments relating to human depth perception provided by this system. The advantages of the system include no reduction in vertical resolution, complete freedom from flicker, full color, and reduced visual fatigue

Stereoscopic depth perception of isoluminant color random—dot stereograms

It has been reported that there is no stereoscopic depth perception under isoluminant color random-dot stereograms (RDS), and that color information does not contribute to human depth perception. This paper describes the results of experiments on stereoscopic depth perception of isoluminant color RDS, obtained by using the prototype flickerless field-sequential stereoscopic television system developed by the present authors. The results of the experiments show that stereoscopic depth perception clearly does exist even in isoluminant color RDS. It was also found that the binocular fusion area on color RDS is about two-thirds that on black/white stimuli, and that the temporal-frequency limits of binocular disparity for the isoluminant color RDS is about 3 Hz, while that for black/white stimuli are 4 to 5 Hz. These results suggest that not only does the luminance channel contribute to human depth perception, but also the chromatic channels.

Usability evaluation of remote controllers for digital television receivers

In order to develop a useful and ergonomically attractive remote controller for ISDB (Integrated Services Digital Broadcasting), which will begin very soon in Japan, we performed experiments with elderly and young subjects to evaluate the usability and the training effects of four types of remote controller: a button type, a trackball, a touch panel and a voice recognition system. We set the subjects the task of selecting an icon on a HDTV monitor as quickly and as accurately as possible using each remote controller. Semantic differential and ranked order questionnaire surveys were also conducted, and these results were analyzed statistically. The results showed that the trackball type was the most preferred, with no major differences in preference among the other three types especially for elderly subjects. From the analyses of the questionnaire surveys and operation time, we conclude that the reasons for the rankings obtained are as follows: Users preferred devices which they could operate without having to look down; Users preferred devices with which there was a significant learning effect in a relatively short period. It is considered that these are necessary conditions for an ergonomically attractive remote controller which users will want to use.

Progressive early decision of speech recognition results by comparing most likely word sequences

The most likely word sequence determined at the end of an utterance constitutes an optimal recognition result in continuous speech recognition for the entire utterance. However, depending on the application, the delay from the utterance to the determination of the recognition result may pose a practical problem, and progressive early decision of recognition results during an utterance becomes necessary. Although in the case of a one-pass search algorithm, progressive early decision of the recognition result by detecting past sole paths during search is possible, an effective early decision scheme is not available for the case of multiple passes. Thus, a scheme for progressive early decision of recognition results by successively comparing the most likely word sequences during an utterance with the past most likely word sequences is proposed and is applied to a one-pass decoder and a two-pass decoder. The proposed scheme attempts to shorten the delays associated with word decisions while limiting the degradation of the recognition rate by controlling the word decision margin and the interval for obtaining the most likely word sequences. In speech recognition experiments of broadcast news, the proposed scheme achieved an average word decision delay equal to that of the past sole path detection method in a one-pass decoder without significantly degrading the word recognition accuracy, and was able to progressively decide recognition results with an average word decision delay time of about 0.5 second in a two-pass decoder.

Visual-Chromatic Spatial and Temporal Frequency Responses in Elderly People

Elderly people tend to perceive color as more yellowish than younger people do, and their ability to discriminate between blueish colors deteriorates as they grow older. This paper describes measurements of visual chromatic spatial and temporal frequency responses in subjects aged 60 to 75 years old to gain a better understanding of age-related changes in color perception and to clarify some differences between young and elderly people. We found that visual chromatic spatial and temporal frequency responses to ayellow-blue (dominant wavelength : 565-445 nm) stimulus were significantly reduced in comparison with those to a red-green (495 nm and its conjugate) stimulus. The results suggest that weakened optical functions in the eye and in the power to send visual signals from the retina to the nervous system are likely causes of this deterioration of color -contrast sensitivity.

Human Visual and Auditory Information. Comprehensibility-based Evaluation of Real-time News Subtitling.

The possibility of real-time subtitling of news programs-using an uncondensed transcription of the words spoken by the newsreader-was considered for people with impaired hearing. Before the system can be created, the effectiveness and preferred format of subtitling need to be investigated. In order to evaluate the comprehensibility of real-time subtitling, subjects with impaired hearing were shown a short news program with subtitles and without sound, and their comprehension of its contents was subsequently tested. Results indicated that the subjects performed about as well after viewing a program with subtitles at the full rate of 280-350 Japanese characters per minute as people with normal hearing did after viewing a program with sound only, and better than after viewing a program with neither subtitles nor sound. Furthermore, they showed no less comprehension than when the subtitles are condensed to 50-70%, as is common broadcasting practice, suggesting that real-time subtitling at full rate is effective for people with impaired hearing.

Sensing of Feeling and "Kansei". Analysis on Blinks while Viewing 3D-HDTV.

Blinking was studied as a physiological index to objectively evaluate the psychological influence of 3D-HDTV images on viewers. Variance of blinking frequency, which indicates the localization of blinks occurring for each cut quantitatively, was used as the method of evaluation. When compared to the variance of blinking frequency while viewing 2D-HDTV images, the results showed that the variance for 3D-HDTV was larger than that for 2D-HDTV. This suggests that the occurence of blinking depends more on the content of each cut for 3D-HDTV than it does for 2D-HDTV. To examine why, cuts that caused frequent blinking are discussed from the viewpoint of interest or concentration. The number of blinks per minute, measured over several cuts, is also investigated. When the viewing time is about 18 minutes, the number of blinks was greater while viewing 3D images than whil eviewing 2D images for one subject tested. For four other subjects tested, however, there was no significant difference in the number of blinks.

50-inch Autostereoscopic 3-D Television.

メガネが不要な50インチ液晶投写型の多眼式3次元カラーテレビジョン装置を試作した.この装置は被写体を4台のテレビカメラで同時に撮像し, 信号処理によって縦縞のストライプ像に合成したあと, 1台の高性能液晶プロジェクタを用いてレンチキュラスクリーンに背面投写する方式である.試作した4眼式3次元テレビジョン装置は, 従来の2眼式に比べて立体視できる観察範囲が拡大し, 自然で見やすい立体カラー動画像を表示することができた.

A real-time measurement system to evaluate image sharpness for CRT display

It is necessary to display clearly characters and figures in addition to ordinary pictures, for CRT displays of computer terminals and high-definition televisions (HDTV). Among the factors constituting image quality of CRTs, image sharpness is important. This paper proposes a method of objective evaluation of the image sharpness of CRT displays, and describes a real-time image-sharpness evaluation system based on this method. In the system, the spatial-frequency characteristics of the whole CRT display are measured quickly using a microprocessor. Then the value of the sharpness under given objective conditions is calculated using both the data observed and a mathematical model of a human-visual system. It was confirmed that the image-sharpness of TV-receivers measured by this evaluation system agrees well with subjective evaluations. The proposed system provides a practical method of evaluating or predicting the image-sharpness of CRT displays.